A drive control apparatus and method drives an AC motor by applying a rectangular wave voltage thereto. The apparatus estimates the torque of a rotor of the AC motor, and detects a torque deviation which is the difference between the estimated torque and a required torque of the motor. A controller controls a state of the rectangular wave voltage applied to the AC motor, through torque feedback control based on the torque deviation, so that the torque approaches the torque command value. The controller detects a current rotation speed of the motor, and switches, in a predetermined order, a plurality of predetermined rectangular wave voltage states corresponding to different phase values of the rectangular wave voltage. The switching timing of the rectangular wave voltage states is set to a timing that deviates from a reference timing determined based on the current rotation speed, by a length of time corresponding to the torque deviation.